How GCC Powers RISC-V Compilers Behind the Scenes

Added: 2026-06-07

[00:00:00]Here's the mental model you need. Think [music] of the RISC-V ISA as a dependency pyramid. Every layer [music] depends on everything below it. At the very bottom, the mandatory foundation, [music] is RV32I or RV64I, the [music] base integer instruction set. Every RISC-V processor must implement this. It's the only thing guaranteed [music] to exist.

[00:00:25]Above that, you add M for multiply and divide, and A for atomics. [music] Together with the base, that gives you RV64IMA, the minimum for any non-trivial computation.

[00:00:39]Then come [music] F and D, single and double precision floating point. When you add all five of these [music] together, I, M, A, F, and D, you get the shorthand G. So, RV64GC [music] means 64-bit, the full G bundle, plus C for compressed 16-bit instructions.

[00:00:59]That's the standard [music] Linux user space baseline.

[00:01:03]Above that sits everything else, the named extensions, like Zeba, ZBB, [music] ZBC for bit manipulation, V for vectors, H for hypervisors.

[00:01:13]Now, here's why [music] this matters for the toolchain.

[00:01:16]The march equal string is not a hint. It is a legally binding [music] contract between you and the compiler. It describes exactly what in